Hand grinding-jig.



E. F. G. GIBBS.

HAND GRINDING JIG.

APPLICATION FILED OCT. 24. 1913.

1,120,926. Patented Dec. 15. 1914.

an bemtoz Wdwwooeo THE NORRIS PEIERS 60.. PHOTUJJTHQ. WASHINGTON. n. c.

UNITED STATES PATENT oriuon EDWARD F. G.'GIBBS, OF WASHINGTON, DISTRICT 01? COLUMBIA.

HAND GRINDING-JIG.

To all whom it may concern I Be it known that I, EDWARD F. GnGiBBs, a'

citizen of the United States, residing at Washington, in the District of Columbia, have invented certain new and useful Im- This invention relates to new and useful improvements in jigs, used for'grinding cut ters, known as inserted cutters, byhand, to a given angle. I do notmean, however, to limit myself to grinding cutters only, or hand use only. It is hereinafter fully described, shown in the accompanying draw ing, and then specifically defined in the appended claims.

The specific object of this invention is to obtain the design of a practical eye gaged and hand controlled jig, which can be manufactured economically and used satisfactorily in grinding internal and external inserted thread cutters to the proper angle on the'face of a rotating grinding wheel; to grind such cutters to an equal angle on both sides, and with cross concave side faces; and for the further purpose of grinding and regrinding the top face of such cutters to a cross concave and to, what is known as, a lip To this end I have designed the mechanism illustrated in the accompanying drawing, which forms a part of this specification and in'which drawing Figure-1 is a plan view of the jig, holding 'a cutter, which has just been ground by the grinding wheelshown. Fig. 2 is an edge view of the jig. Fig. 8 is a plan view of the cutter end of the jig, holding ,a cutter which is about to be cross concaved'and lipped on topby a grinding wheel, shown.

Fig. l is an edge view of the cutter-holding strap. Fig. 5 is a plan of the'angle block,

or angle piece. Fig. 6 is a front endview of the angle block. Fig. 7 is an edge view of the angle block, showing the triangular channel, and section of cutter therein. 8 is a-plan'view of an inserted cutter which" has'been ground. Fig. 9 is a side elevation of an inserted critter which has been ground;

and lipped. Fig. 10 is a view of a cutter from the ground end. Fig. 11 is an angular side elevation of a cutter, as seen froma' point in a line projected from oneof the concaved' angular cutting faces.

Reference now being had to the details of the 'drawingby letter, A designates thetop and bottom frame pieces,'.or the, frame} The Specification of Letters Patent. Patented De 15 1914 Application filed. October 24, 1913. Serial No. 797,107. if I jig being skeleton in form and open-sided, there are no slde frame pieces.

B designates the angle blockor angle cs' o piece carried between the frame pieces at their front en'd,"the front end or, front face,

preferably of which, angle piece, carries the triangular channel or 'guide b, which channel or guidein fixedrelationship to the frame governsthe angle at which the cutter 1s ground. It also 'carries the rectangular channels, 6 which are covered and pr0- tected by the frame pieces. C designatesa' cutter which is held the said channel to be ground. D designates agrinding wheel with p which the said'cutter is ground.

E designates the strap the end of whichis inclined to agree with the incline of the channel, I), and havingtwo arms, 6, adapted" to fit loosely in the rectangular channels, Z2 of the angle'blo'ck. Itembraces thesaid angle block, triangular channel and cutter in sliding relation'thereto and holds the said cutter, while being ground. 6 designates the rectangular union plug to which. the rear ends of both arms nut f.

It is to beobserved that when this jig is used" as a hand jig, itis practically in the same plane with the axial center of thegrinding' wheel, horizontally disposed and the eyealone is used to gage the position of its rear end, both horizontally, and vertiare joined. Said strap is drawn against the cutter by F, the screw-threaded rod,andj the v cally; the front end'being supported by the rest carried by all hand grinders. 'It is adapted to eye gage and hand control, because it is long, slender, lightaind straight.

It is of rectangular plan and cross-sectional figure, with no obstructions to distract the vision. Therefore it can beheld at a right angle to, or square with the face of a grinding wheel,,as shown in Fig. 1,.w1th much I greater accuracy than the cutter can held at an angle of, say, 30degrees. The vision is remarkably accuratein forming aright angle by intersecting onestraight line with another, b'ecause informing one right angle another 'isfor ned also, and comparison is natural;

be observed that the function of the angle tionship between the cutter to be ground and i nal angle, which gives the angle to the 'wall of the thread, and the vertical angle, which gives clearance to the cutter, are obtained by eye gage. and hand control of the jig. Note also that the protected strap, E, which embraces both the angle piece, B, and cutter, C, is far preferable to a yoke which would penetrate the angle piece and embrace the cutter; for the reason that in grinding short cutters, in which the jig is most needed, the rear ends would be drawn into the hole in which the yoke worked.

It is quite possible and practicable, :perhaps, to evade the exact construction shown here, eliminate the angle block and strap entirely, and substitute therefor, among other things, integral portions of the frame itself, without deserting the principle of a fixed angular relationshipbetween the cutter and frame. Against such infringement I desire to be protected, if I am the real inventor.

When one side of a cutter held by the jig is ground as shown in Fig. 1, the jig being held," by hand, or otherwise, the cutter is then turned upside down in the jig,-and thewhich, turning, would cause the clearance angles ofthe two sides to be ground unequal; while the face of the angle block, B, is provided witha triangular channel, I), which receives and holds a square cutter of any size, within its range, sothat its end cannot be drawn down bythe grinding wheel. Furthermore, it is necessaryfor a jig of this nature to be of rectangular cross sectional figure, or flat bottomed, in order to sit steady on the grinder rest, and grind both sides equal. When a cutter has once been thus properly ground on its sides, it should be regarded as a formed cutter and sharpened when dull by grinding it on top only, as shown in Fig. 3.

Indeed, a cutter is not ready for advantageous use until it is ground on top as shown in Fig. 3.

One great advantage incident to the use of this jig is that it aids the operator in holding the cutter practically in the same horizontal plane with, and vertically parallel to, the axial center of the grinding wheel, the face of which grinds it. Thus the ground faces are crossconcaved slightly, by the curvature of the wheel, as shown in Figs. 3, 9, 10, 11. Both sides of the two cutting edges being concaved they are particularly keen, cut rapidly and leave a smooth thread. Another advantage incident thereto, particularly noticeable in regrinding small short cutters for internal thread cutting, is that it facilitates grinding what is known as a lip onthe cutter, as shown in Fig. 9.

This jig is made in skeleton form, the framing and all parts being light, for the chief purpose of making it as light and wieldy as practicable. same reason and for the further purpose of enabling the operator to use common washers for clamps in clamping it to the table of a cutter grinder, and thus clamp it without danger of crushing it. The presence of the union plug, e makes the strap end less, and enablesthe applicant, at pleasure, to tap out the rod hole and convert'the rod, F, and nut, f, into a long'thumb screw. The frame pieces of this construction also furnish the much needed cover and protection to the strap arms.

- Having fully described my invention, I desire to secure by Letters Patent what is new according to the following claims:

1. Athread-cutter grinding jig, adapted It is made open-sided for the to eye-gage and hand-control; comprlsing a skeleton frame; an angle piece, carried by the said frame, adapted to receive a cutter to be ground and fix the specific angular relationship between it and the said jig; a strap embracing the said angle piece and cutter; and-means for holding the said strap against the said cutter while it is being ground; all substantially as set forth.

a 2. A thread cutter grinding-jig, adapted to eye-gage and hand-control; compris ng an open-sided frame; an angle-piece carried by the said-frame, adapted to receive a cutter to be ground and fix the specific angular relationship between it and the said jig; and means for holding the said cutter against the said angle piece while it is being ground; all substantially as set forth.

3. A thread-cutter grinding jig, adapted to eye-gage and hand-control; comprising a framep an angle piece, carried by the said frame, having a channel in its front face adapted to receive a cutter to be ground,

havingalso side channels covered and protected by the said frame and adapted to receive the arms of a strap; a strap. having arms fitted to the said covered and protected channels, in sliding relation thereto and embracing the said angle piece and cutter; and means for holding the said strap against the said cutter While it is being ground; all substantially as set forth.

4. A thread-cutter grinding-jig, adapted to eye-gage and hand-control; comprising a skeleton frame; an angle piece carried by the said frame adaptedto receive a cutter to be ground; a StI'HP,Wl1OS6 arms are covered and protected by the said frame, embracing the said angle piece'and cutter; and means for holding the said strap against the said cutter Whileit is being ground; all substantially as set forth. I p

5. A thread-cutter grinding jig, adapted to eye-gage and hand-control; comprising an open-sided frame; an angle piece carried by the said frame, adapted to receive a cutter to be ground; a strap, Whose arms are covered and protected by the said frame, embracing the said angle piece and cutter; and means for holding the said strap against the said cutter While it is being ground;all

substantially as set forth.

6. A thread-cutter grinding-jig, adapted to eye-gage and hand-control; comprising a skeleton frame; an angle piece, carried by the said frame, adapted to receive a cutter to be ground; a strap, hose arms are joined to a union plug at their rear ends,

embracing the said angle piece and cutter; and means for holding the said strap against the said cutter While it is being ground; all

substantially as set forth;

7. A thread-cutter grmdingjig adapted to eye-gage and hand-control; comprising a frame; an angle piece, carried by the nation of a frame having flat top and botj tom; an angle block carried by the said frame, having in itsfront face a triangular channel adapted to receive a cutter to be ground; a strap having a-fiat bottom, embracing the said angle block and cutter; and meansfor holding the said strap against the said cutter While it is being ground; all substantially as set forth.

In testimony whereof I affix my signature in presence of tWo Witnesses.

EDWARD F. s, GIBBS. Witnesses E. L. ABRAMs, A. E. MONROE.

Copies of this patent may be obtained for five cents each, by addre i the commissioner of Patents,

Washington, I), (3," 

